I guess you used soap or soap powder. Calcium and magnesium ions in water and soap generate calcium-white fatty acid suspensions, which are deposited on clothes and turn white one by one. It wouldn't be so obvious if it weren't for black clothes. If so, it can be treated with special silk wool net and phosphorus-containing washing powder. Note that I am talking about phosphorus-containing washing powder. The decontamination and Shui Rou ability of phosphorus-free washing powder is far from that of phosphorus-containing washing powder! Mix a small amount of these two detergents, dissolve them in warm water, put them in clothes, rub them gently, and then dry them thoroughly, which should wash off the white marks to the maximum extent. If there is no silk wool net, you can also use shampoo instead. universal network